Onchocerciasis affects approximately 20 million people. It remains a major cause of blindness n the world and continues to contribute to economic deprivation in much of its endemic range. The prospects for controlling onchocerciasis have improved with the introduction of the microfilaricide ivermectin. However, resistance to insecticides used in vector control is now widespread and there remains a pressing need to develop macrofilaricidal compounds and/or vaccines. As a background to drug and vaccine development much still needs to be learned concerning the development of pathology, and eye disease in particular. Autoantibodies to retinal S-antigen have been reported from onchocerciasis patients. Experimental autoimmune uveoretinitis (EAU) in lab animals can be induced with S-antigen and with interphotoreceptor retinol-binding protein (IRBP). There are some similarities between retinal disease in human and experimental onchocerciasis and IRBP-induced EAU. The detection of parasite retinol binding protein (PRBP) and parasite retinoic acid binding protein PRABP) in Onchocerca has implied a possible role for these proteins in retinal disease. The working hypothesis for this study is that PRBP, or portions of the protein, liberated from dead parasites, induce autoimmune pathology in the host. The aims of this study are to: a). clone and sequence the PRBP (and PRABP) gene and express and produce PRBP in vitro; b). demonstrate the presence of anti-PRBP and antiretinal antibodies in mouse and human sera; and c). demonstrate that injection of PRBP into mice leads to retinal disease. The long-term goals of this study are to sequence the PRBP gene and to demonstrate a correlation between anti-PRBP antibodies and onchocercal retinal disease. Additionally since one of the major mechanism for the action of ivermectin appears to be through blocking binding of retinol to PRBP, sequencing the PRBP may provide useful information on this blocking action. The experimental methodology to be followed includes standard molecular biological (cDNA library construction and screening, sequencing and protein expression) immunological (ELISA, western blot, antigen inoculation) and clinical (slit-lamp observations and histology of mouse eyes) techniques.